ROLE OF FIRE IN CALIFORNIA PINE FORESTS 45 
As a change from extensive grain growing to intensive agriculture 
develops further in the great Galfiona valleys, the importance of an 
adequate and sustained supply of water for irrigation becomes more 
and more imperative. In some places, irrigation is the very essence 
of intensive agriculture, as in the citrus belt of southern California. 
As the valleys of the Sacramento and San Joaquin Rivers are more 
intensively used, the need for a conservation of irrigation water will 
become more and more apparent. 
The ways in which destruction of the mountain cover damages 
agriculture are the same in California as in other parts of the world, 
as many thorough investigations have shown. Reduction of the low- 
water stage of streams, the lowering of the water table, and the silt- 
ing up of valley agricultural lands, reservoirs, and ditches are princi- 
pal effects of forest destruction and are particularly important in 
regions dependent upon irrigation. 
he great hydroelectric development now under way in the Cali- 
fornia mountains may also be adversely affected by the removal of 
the forest cover, as silting of reservoirs and the disturbance of run- 
off reduce the amount of power developed. 
The tendency to ignore or undervalue the intimate relation between 
forest and brush cover on the one hand and agriculture and power 
development on the other has resulted from two principal conditions: 
(1) The supply of water for relatively extensive agriculture has been 
so abundant that there has been no need to take thought of the con- 
servation of thesupply. (2) The present point of use of water has been 
so far removed from the watersheds themselves that the water users 
enerally have failed to recognize that what may affect a far distant 
forsee or brush cover is of vital importance to them. The interests 
of the valley agriculturists are sharply in conflict with those of the 
farmer or grazier in the brushy foothill region who shortsightedly 
desires the wholesale removal of cover by burning. 
In short, although water may be used at a point far removed from 
an area suffering from forest destruction and the effects of forest de- 
struction may not be immediately evident in their relation to the 
water supply, it can not be doubted that this secondary value of the 
forests is an important consideration in California as elsewhere. 
LIGHT BURNING 
TECHNIQUE 
Light or controlled burning may be defined as the intentional burn- 
ing of the forest at intervals, witli the object of consuming much of 
the inflammable material and of so reducing the general forest-fire 
hazard that accidental fires will be controlled with ease and will cause 
but mininum damage to merchantable timber. We must, then, dis- 
tinguish between light or controlled burning proper, which has the 
specific objective of protecting forests, and general or promiscuous 
forest. burning, which disregards forest values and aims to improve 
grazing, facilitate prospecting, and render the forest more accessible. 
The technique of light burning has varied somewhat during the last 
15 years. Different practitioners have evolved different methods, 
both for controlling the fires themselves and their effect on merchant- 
able timber. In general, however, the fires are set either in spring or 
